/*
 * Copyright (C) 2016 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.graph;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.graph.GraphConstants.EDGE_CONNECTING_NOT_IN_GRAPH;
import static com.google.common.graph.GraphConstants.GRAPH_STRING_FORMAT;
import static com.google.common.graph.GraphConstants.NODE_NOT_IN_GRAPH;

import com.google.common.annotations.Beta;
import com.google.common.base.Function;
import com.google.common.collect.Maps;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;

/**
 * This class provides a skeletal implementation of {@link ValueGraph}. It is recommended to extend
 * this class rather than implement {@link ValueGraph} directly.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <V> Value parameter type
 * @since 20.0
 */
@Beta
public abstract class AbstractValueGraph<N, V> extends AbstractBaseGraph<N> implements ValueGraph<N, V> {

    @Override
    public Graph<N> asGraph() {
        return new AbstractGraph<N>() {
            @Override
            public Set<N> nodes() {
                return AbstractValueGraph.this.nodes();
            }

            @Override
            public Set<EndpointPair<N>> edges() {
                return AbstractValueGraph.this.edges();
            }

            @Override
            public boolean isDirected() {
                return AbstractValueGraph.this.isDirected();
            }

            @Override
            public boolean allowsSelfLoops() {
                return AbstractValueGraph.this.allowsSelfLoops();
            }

            @Override
            public ElementOrder<N> nodeOrder() {
                return AbstractValueGraph.this.nodeOrder();
            }

            @Override
            public Set<N> adjacentNodes(Object node) {
                return AbstractValueGraph.this.adjacentNodes(node);
            }

            @Override
            public Set<N> predecessors(Object node) {
                return AbstractValueGraph.this.predecessors(node);
            }

            @Override
            public Set<N> successors(Object node) {
                return AbstractValueGraph.this.successors(node);
            }

            @Override
            public int degree(Object node) {
                return AbstractValueGraph.this.degree(node);
            }

            @Override
            public int inDegree(Object node) {
                return AbstractValueGraph.this.inDegree(node);
            }

            @Override
            public int outDegree(Object node) {
                return AbstractValueGraph.this.outDegree(node);
            }
        };
    }

    @Override
    public V edgeValue(Object nodeU, Object nodeV) {
        V value = edgeValueOrDefault(nodeU, nodeV, null);
        if (value == null) {
            checkArgument(nodes().contains(nodeU), NODE_NOT_IN_GRAPH, nodeU);
            checkArgument(nodes().contains(nodeV), NODE_NOT_IN_GRAPH, nodeV);
            throw new IllegalArgumentException(String.format(EDGE_CONNECTING_NOT_IN_GRAPH, nodeU, nodeV));
        }
        return value;
    }

    @Override
    public final boolean equals(@Nullable Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof ValueGraph)) {
            return false;
        }
        ValueGraph<?, ?> other = (ValueGraph<?, ?>) obj;

        return isDirected() == other.isDirected() && nodes().equals(other.nodes())
                && edgeValueMap(this).equals(edgeValueMap(other));
    }

    @Override
    public final int hashCode() {
        return edgeValueMap(this).hashCode();
    }

    /** Returns a string representation of this graph. */
    @Override
    public String toString() {
        String propertiesString = String.format("isDirected: %s, allowsSelfLoops: %s", isDirected(), allowsSelfLoops());
        return String.format(GRAPH_STRING_FORMAT, propertiesString, nodes(), edgeValueMap(this));
    }

    private static <N, V> Map<EndpointPair<N>, V> edgeValueMap(final ValueGraph<N, V> graph) {
        Function<EndpointPair<N>, V> edgeToValueFn = new Function<EndpointPair<N>, V>() {
            @Override
            public V apply(EndpointPair<N> edge) {
                return graph.edgeValue(edge.nodeU(), edge.nodeV());
            }
        };
        return Maps.asMap(graph.edges(), edgeToValueFn);
    }
}
